On demand drinking water systems are known. In one type of system a reverse osmosis unit is used to treat and subsequently dispense relatively small quantities of treated water. In many currently available systems, the time it takes to fill a glass with the treated water can be unacceptably long. Consumers desire water treatment systems that dispense treated water quickly and which do not rely on external power for their operation.
Reverse osmosis-based water treatment systems that do not require external power are known. An example of such a system is described in U.S. Pat. Nos. 4,650,586 and 6,764,595 which are both owned by the assignee of the present application and which are hereby incorporated by reference. The systems disclosed in these two patents have proven successful. However, consumers desire systems capable of producing and/or dispensing treated water at larger flow rates.